88
votes
Accepted
Why does Io cast a hard shadow on Jupiter, but the Moon casts a soft shadow on Earth?
It's due to the larger relative apparent size of the Sun. When the source of light is a point source the shadow is harder, and when it is extended it is softer.
Jupiter is approximately 5 times more ...
- 3,158
51
votes
Accepted
How precise are future Solar eclipse timing, path and dates, what could change timing/path?
For the past few decades, the best eclipse data has been produced by Fred Espenak, aka Mr Eclipse. Fred is a former employee of NASA's GSFC. He's retired now, but he still maintains an excellent ...
- 16.7k
47
votes
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Counting from the 21st century forward, what place on Earth will be last to experience a total solar eclipse?
Here is a combination of the maps available from NASA SEAtlas. They cover time span from year 2001 to 3000. Made with a custom Python script and some editing in GIMP.
The yellow to blue colors mark ...
- 1,680
46
votes
Can a lunar eclipse happen at night and be followed by a solar eclipse the next day?
No.
A lunar eclipse occurs when the moon is on the opposite side of the Earth as the sun.
A solar eclipse occurs when the moon is on the same side of the Earth as the sun. And it takes the moon 14 ...
- 130k
45
votes
Accepted
Why is there a year 1 B.C., a year 0, and a year 1 A.D. in NASA’s Five Millennium Canon of Solar Eclipses?
This is all explained on the home page All dates are astronomical dates. These match CE (or AD) dates for positive values but differ by 1 for BCE dates.
The Gregorian calendar is used for all dates ...
- 130k
41
votes
Is it possible that the shadow of The Moon is a single dot during solar eclipse?
What you are calling a focal point is the end of the umbra, the point at which the umbra changes to the antumbra. In a total solar eclipse, that point is below rather than above the surface of the ...
- 36.3k
39
votes
Can a planet in our system eclipse the sun as seen from another one?
In our solar system, it is possible for one planet to partially eclipse the sun, but it is not possible for any planet to cause a full solar eclipse as seen from another planet.
The sun is too big and ...
- 16.7k
36
votes
Why is the lunar relief not visible in photographs of solar eclipses?
In short, you would need a very high resolution photo -- most likely taken through a telescope -- to identify any surface features on the moon by their effect on the limb (that is, the edge of the ...
- 5,820
35
votes
Accepted
Will just a glimpse (less than a second) of sun during partial solar eclipse damage eyes?
Glancing at a partial solar eclipse is about as dangerous as glancing at the Sun on any other day. If you look at the Sun a few minutes after sunrise or a few minutes before sunset, when the Sun's ...
- 16.7k
32
votes
Why does Io cast a hard shadow on Jupiter, but the Moon casts a soft shadow on Earth?
Due to the basic proportionality theorem, the width of the boundary of the shadow is
$$
w=\frac{\ell D}L\;,
$$
where $\ell$ is the distance from the moon to the planet’s surface, $L$ is the ...
- 421
32
votes
Accepted
How do I know it is safe to remove eclipse glasses when viewing a total solar eclipse?
Eclipse glasses are so dark that nothing can be seen through them, except the surface of the sun.
When you are looking through the eclipse glasses, if you can see any part of the sun at all, it is ...
- 130k
30
votes
Is it possible to see mercury transit "clearly" by the naked eye?
I did see the Venus transit before the Sun in 2004.
I used no telescope, but of course I used proper solar eclipse glasses to protect my eyes. The black circle was small but clearly visible.
But ...
- 411
29
votes
Why is it okay to watch a sunset but not an eclipse?
During a sunset, the Sun is lower in the sky than during most of the day - much lower. Therefore, light from the Sun travels through about 120 miles of dense atmosphere, compared to the roughly 2 ...
- 37.4k
29
votes
Accepted
What do Saturn's rings look like during a total solar eclipse, viewed from one of its moons?
Cassini (the orbiter) has captured images of Saturn with the sun in eclipse:
The rings are back-lit, They self-shadow quite well but not enough to completely block sunlight, so appear bright against ...
- 130k
27
votes
Accepted
Is it possible to see mercury transit "clearly" by the naked eye?
I'll use the atmosphere as my big natural lens. So I'll watch the upcoming mercury transit at the sunset time where the sun looks bigger than usual.
While the Sun and Moon might seem larger at the ...
- 30.7k
26
votes
Accepted
What caused pink flares during the eclipse
That would have been the so called 'solar prominences' i.e. eruptions of plasma on the surface of the Sun (see https://www.iflscience.com/next-months-total-solar-eclipse-could-come-with-bright-pink-...
- 3,611
25
votes
Accepted
Was the Sun's gravitational lensing observed in other solar eclipses than the one in 1919?
Yes, observations of this kind are within the technical scope of amateur astronomers. Several groups succeeded in replicating the experiment during the 2017 eclipse that crossed the USA.
For example ...
- 130k
24
votes
During an eclipse, how big is the shadow of the moon on the earth?
But how big is this shadow? How many kilometers is its diameter?
That's a photo of the umbra and penumbra on the surface of the Earth taken from Space. It's a little distorted because it's not ...
- 30.7k
22
votes
Can a planet in our system eclipse the sun as seen from another one?
The short answer is no. The alignment occurs, but the eclipse does not, due to the distances and size differences involved.
There are a few things to consider here. You already mentioned a lot of them,...
- 381
20
votes
Accepted
During an eclipse, how big is the shadow of the moon on the earth?
The umbra has a well defined diameter but the size varies due to the eccentricity of the orbits of the Earth and of the Moon. The Moon may be so far away that it can't fill the solar disk at all (for ...
- 408
20
votes
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Orbit of the moon so that there are no eclipses
Answer: yes, a no-eclipse orbit is possible
The plane of the Earth-Sun orbit (the ecliptic) and the plane of the Earth-Moon orbit must intersect each other because they both contain at least one point ...
- 1,257
20
votes
Accepted
During a total solar eclipse is it possible to see solar flares with the naked eye?
If by 'solar flare' you mean a coronal mass ejection, then yes, in theory you could see one during a total eclipse if there happened to be one that was at approximately 90 degrees to Earth at the time ...
- 5,820
18
votes
Apparently two objects in Solar Eclipse image
The people who say it is an internal reflection are right. This is an internal reflection inside the lens of the camera. There is no actual object there. In particular, Venus is not visible this ...
- 130k
18
votes
Accepted
Apparently two objects in Solar Eclipse image
It's an internal reflection. The dead giveaway is that in the second picture, the reflected image is a point reflection at the center of the image optical axis (assuming the image was not cropped).
...
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18
votes
The darkness that is equivalent to the block of 99.5% of the sun
This misses the point.
During totality the sun's corona becomes visible. If any part of the photosphere is exposed, then the corona isn't visible.
The experience of a total eclipse is not just "...
- 130k
18
votes
The darkness that is equivalent to the block of 99.5% of the sun
I agree with James K's observation that the main point of a total eclipse is not the darkness but the visibility of the corona.
However, to answer your original question, blocking 99.5% of the Sun* ...
- 677
17
votes
Counting from the 21st century forward, what place on Earth will be last to experience a total solar eclipse?
Short answer is that no one knows, there's too much margin for error.
There is too much margin for error, just in the Earth's rotation. The Earth does not rotate at a constant rate, partly due to the ...
- 6,207
16
votes
Why can't we see a solar eclipse every month?
The Moon orbits in a plane that is inclined with respect to the plane in which the Earth orbits. The intersection between these two planes is a straight line. For an eclipse to occur, this straight ...
- 17.8k
15
votes
Is it possible that the shadow of The Moon is a single dot during solar eclipse?
As the Moon's eccentric orbit around the Earth brings it nearer and farther, current solar eclipses can be total or annular.
A few in between are
hybrid eclipses: total along the midday part of the ...
- 18.8k
14
votes
Will just a glimpse (less than a second) of sun during partial solar eclipse damage eyes?
This webpage gives a lot of background information. Key points:
It does seem to be the overall dimness of near-total eclipses that allows the pupil to widen enough to allow damaging levels of UV in.
...
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Only top scored, non community-wiki answers of a minimum length are eligible